Paging for csfb in lte connected mode

ABSTRACT

Methods, apparatuses and computer readable media are described that analyze and communicate signaling messages between a mobile wireless device and a wireless access network to realize a circuit switched fallback (CSFB) procedure when the mobile wireless device is initially in a radio resource control connected mode with the wireless network. A set of information elements of a paging message is analyzed, and based on contents of the set of information elements and an internal state of the mobile wireless device, connections between the mobile wireless device and first and second wireless access networks are changed to realize the CSFB procedure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/657,767, filed Jun. 9, 2012 and entitled “PAGING FOR CSFB IN LTECONNECTED MODE,” and which is incorporated by reference herein in itsentirety for all purposes.

TECHNICAL FIELD

The described embodiments generally relate to methods and apparatusesfor managing radio connections between mobile wireless devices and oneor more wireless networks. More particularly, the present embodimentsdescribe signaling between a mobile wireless device and a wirelessnetwork to realize a circuit switched fallback (CSFB) procedure when themobile wireless device is initially in a radio resource control (RRC)connected mode with the wireless network.

BACKGROUND

Wireless networks continue to evolve as new communication technologiesdevelop and standardize. Wireless network operators can deploy newcommunication technologies in parallel with earlier generationcommunication technologies, and wireless networks can support multiplecommunication technologies simultaneously to provide smooth transitionsthrough multiple generations of mobile wireless devices. Mobile wirelessdevices can include hardware and software to support wirelessconnections to different types of wireless networks that use differentwireless communication technologies. Wireless networks using differentradio access technologies (RATs) can overlap in geographic areacoverage, and mobile wireless devices can support connections usingdifferent RATs depending on services and/or coverage available. Awireless service provider can provide services to mobile wirelessdevices through overlapping wireless networks, and mobile wirelessdevices can connect to one or more of the overlapping wireless networks.In a representative embodiment, a wireless service provider and/or amobile wireless device can include simultaneous support for a ThirdGeneration Partnership Project (3GPP) Long Term Evolution (LTE) wirelesscommunication protocol and a “legacy” third generation (and/or earliergeneration) wireless communication protocol. Representative “legacy”protocols include the Third Generation Partnership Project 2 (3GPP2)Code Division Multiple Access (CDMA) 2000 1× (also referred to as 1×RTTor 1×) wireless communication protocol, the 3GPP Universal MobileTelecommunications System (UMTS) wireless communication protocol, andthe 3GPP Global System for Mobile Communications (GSM) wirelesscommunication protocol.

Mobile wireless devices can include a combination of hardware andsoftware to connect to multiple wireless networks that use differentwireless communication protocols. Representative mobile wireless devicescan support circuit switched (CS) voice connections through a firstwireless access network that uses a legacy wireless communicationsprotocol, e.g., the CDMA 2000 1× wireless communication protocol, andpacket switched (PS) connections (voice or data) through a secondwireless access network that uses the LTE wireless communicationprotocol. Additional representative mobile wireless devices can supportCS voice connections through a UMTS wireless network or through a GSMwireless network and can support PS data or voice connections through anLTE wireless network. In some embodiments, the LTE wireless networkand/or the mobile wireless device can be unable to support PS voiceconnections (yet able to support PS data connections), and the mobilewireless device can use a CSFB procedure to revert to a CS voiceconnection through a legacy wireless network. The mobile wireless devicecan operate in cooperation with the LTE wireless network and with thelegacy wireless network to suspend a PS data connection with ordisconnect from the LTE wireless network to originate or terminate a CSvoice connection through the legacy wireless network, e.g., through aCDMA 2000 1× wireless network, a UMTS wireless network, or a GSMwireless network. While the mobile wireless device can use the LTEwireless network for PS data connections, when the mobile wirelessdevice originates an outgoing voice connection or responds to anincoming voice connection, the mobile wireless device can transitionfrom using the LTE wireless network to using a legacy wireless networkthat supports CS voice connections. When the CS voice connectioncompletes, the mobile wireless device can subsequently return to the LTEwireless network for PS data connections.

The 3GPP standardized LTE wireless communication protocol specifiesmultiple options for CSFB procedures including messages and responsesfor when a mobile wireless device is in different connection states withthe LTE wireless network. The LTE wireless communication protocolincludes two possible connection states that can exist between themobile wireless device and the LTE wireless network, namely a radioresource control (RRC) connected state and an RRC idle state. The CSFBprocedures for each connection state can differ in the sequence ofmessages and responses communicated between the mobile wireless deviceand the LTE wireless network. In certain circumstances, the mobilewireless device and the LTE wireless network can become misaligned withrespect to each other concerning the connection state that existsbetween them, e.g., the mobile wireless device can assume an RRCconnected state exists with the LTE wireless network, while the LTEwireless network can assume an RRC idle state exists with the mobilewireless device. Following the standardized CSFB procedures, the LTEwireless network can send one or more messages to the mobile wirelessdevice based on a first connection state, and the mobile wireless devicecan ignore the one or more messages from the LTE wireless networkbecause it assumes a second different connection state. In such ascenario, the mobile wireless device can miss an incoming voiceconnection indicated by the LTE wireless network because of themisaligned connection states between the mobile wireless device and theLTE wireless network. Thus, there exists a need for a method to supportalternate CSFB procedures to establish mobile terminated voiceconnections when the mobile wireless device is in one connection state,e.g., an RRC connected state, and the LTE wireless network assumes adifferent connection state, e.g., an RRC idle state.

The teachings described herein can be applied to mobile wireless devicesthat can operate in dual (or more generally multiple) wirelesscommunication technology networks. In particular, the teachingsdisclosed herein can pertain to mobile wireless devices that switch fromusing one wireless technology for a first connection (e.g., a PS dataconnection) to another wireless technology for a second connection(e.g., a CS voice connection).

SUMMARY OF THE DESCRIBED EMBODIMENTS

The described embodiments generally relate to methods and apparatusesfor managing radio connections between mobile wireless devices and oneor more wireless networks. More particularly, the present embodimentsdescribe signaling between a mobile wireless device and a wirelessnetwork to realize a circuit switched fallback procedure when the mobilewireless device is initially in a radio resource control connected modewith the wireless network.

In an embodiment, a method to respond to paging messages by a mobilewireless device is described. The method includes at least the followingsteps executed by the mobile wireless device. The mobile wireless devicereceives a paging message from a first wireless network. The mobilewireless device determines that the paging message includes a firstinformation element that uniquely identifies the mobile wireless device.The mobile wireless device also determines that the paging messageincludes a second information element that indicates the paging messageoriginates from a second wireless network. The mobile wireless devicefurther determines that the paging message does not include a thirdinformation element that indicates the paging message is a publicwarning system message. When an internal state of the mobile wirelessdevice indicates that the mobile wireless device is connected to thefirst wireless network, after receiving the paging message and afterdetermining that the paging message includes the first and secondinformation elements and does not include the third information element,the mobile wireless device disconnects from the first wireless networkand establishes a connection to the second wireless network. In arepresentative embodiment, the first wireless network operates accordingto an LTE wireless communication protocol, and the second wirelessnetwork operates according to a non-LTE wireless communication protocol.

In another embodiment, a mobile wireless device is described. The mobilewireless device includes at least one or more processors, one or moretransmitters, and one or more receivers. The one or more processors areconfigured to control establishing and releasing connections between themobile wireless device and a first wireless network and a secondwireless network. The one or more transmitters are configured totransmit signals to the first wireless network according to a firstwireless communication protocol and to the second wireless networkaccording to a second wireless communication protocol. The one or morereceivers are configured to receive signals from the first and secondwireless networks. The one or more processors are further configured toobtain a paging message received by the one or more receivers from thefirst wireless network. The one or more processors are configured todetermine that the paging message includes a first information elementthat uniquely identifies the mobile wireless device. The one or moreprocessors are also configured to determine that the paging messageincludes a second information element indicating that the paging messageoriginates from the second wireless network. The one or more processorsare additionally configured to determine that the paging message doesnot include a third information element indicating the paging message isa public warning system message. When an internal state of the mobilewireless device indicates that the mobile wireless device is connectedto the first wireless network, upon receipt of the paging message, andwhen the paging message includes the first and second informationelements and does not include the third information element, the one ormore processors of the mobile wireless device are configured todisconnect the mobile wireless device from the first wireless networkand establish a connection of the mobile wireless device to the secondwireless network. In a representative embodiment, the second informationelement indicates that the second wireless network is a circuit switched(CS) network and that the first wireless network is a packet switched(PS) network.

In another embodiment, a computer program product encoded as computerprogram code in a non-transitory computer readable medium for respondingto paging messages by a mobile wireless device is described. Thecomputer program product includes at least the following computerprogram code. Computer program code for receiving a paging message froma first wireless network. Computer program code for determining that thepaging message includes a first information element that uniquelyidentifies the mobile wireless device. Computer program code fordetermining that the paging message includes a second informationelement indicating that the paging message originates from a secondwireless network. Computer program code for determining that the pagingmessage does not include a third information element indicating that thepaging message is a public warning system message. Computer program codefor, when an internal state of the mobile wireless device indicates thatthe mobile wireless device is connected to the first wireless networkupon receiving the paging message and after executing the computerprogram code for determining that the paging message includes the firstand second information elements and does not include the thirdinformation element, disconnecting the mobile wireless device from thefirst wireless network and establishing a connection of the mobilewireless device to the second wireless network. In a representativeembodiment, the computer program code for disconnecting the mobilewireless device from the first wireless network comprises computerprogram code for releasing a first radio resource control (RRC)connection to the first wireless network locally in the mobile wirelessdevice. In a further representative embodiment, the computer programcode for disconnecting the mobile wireless device from the firstwireless network comprises computer program code for establishing asecond RRC connection to the first wireless network, computer programcode for sending an extended service request message to the firstwireless network, the extended service request message indicating apositive circuit switched fallback (CSFB) response to the pagingmessage, and computer program code for receiving a signaling messagefrom the first wireless network, the signaling message indicatingrelease of the second RRC connection and redirection of the mobilewireless device to the second wireless network.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments and the advantages thereof may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings.

FIG. 1 illustrates components of a generic wireless communicationnetwork.

FIG. 2 illustrates components of a CDMA 2000 1× (RTT or EV-DO) wirelesscommunication network.

FIG. 3 illustrates components of an LTE (or an LTE-Advanced) wirelesscommunication network.

FIG. 4 illustrates a mobile wireless device communicating in parallel tothe CDMA 2000 1× (RTT or EV-DO) wireless communication network of FIG. 2and the LTE (or the LTE-Advanced) wireless communication network of FIG.4.

FIG. 5 illustrates elements of a representative single signal processingchip mobile wireless device.

FIG. 6 illustrates elements of another representative single signalingprocessing chip mobile wireless device.

FIG. 7 illustrates a prior art signaling message exchange between amobile wireless device in an RRC idle state and an LTE wireless networkto realize a CSFB procedure.

FIG. 8 illustrates a prior art signaling message exchange between amobile wireless device in an RRC connected state and an LTE wirelessnetwork to realize a CSFB procedure.

FIG. 9 illustrates another prior art signaling message exchange betweena mobile wireless device in an RRC connected state and an LTE wirelessnetwork in an idle state resulting in an unsuccessful CSFB procedure.

FIG. 10 illustrates a representative embodiment of a method to respondto paging messages received from a first wireless network by a mobilewireless device.

FIGS. 11 and 12 illustrate representative embodiments of method steps todisconnect the mobile wireless device from the first wireless networkapplicable to the method of FIG. 10.

FIG. 13 illustrates a representative embodiment of method steps toestablish a connection between the mobile wireless device and a secondwireless network applicable to the method of FIG. 10.

DETAILED DESCRIPTION OF SELECTED EMBODIMENTS

Representative applications of methods and apparatuses according to thepresent disclosure are described in this section. The examples presentedare provided solely to add context and aid in the understanding of thedescribed embodiments. It will thus be apparent to one skilled in theart that the described embodiments may be practiced without some or allof these specific details. In other instances, well known process stepshave not been described in detail in order to avoid unnecessarilyobscuring the described embodiments. Other applications are possible,such that the following examples should not be taken as limiting.

In the following detailed description, references are made to theaccompanying drawings, which form a part of the description and in whichare shown, by way of illustration, specific embodiments in accordancewith the described embodiments. Although these embodiments are describedin sufficient detail to enable one skilled in the art to practice thedescribed embodiments, it is understood that these examples are notlimiting; such that other embodiments may be used, and changes may bemade without departing from the scope of the described embodiments.

Wireless networks continue to evolve as network operators deployequipment for new wireless communication technologies based on ongoingstandardization efforts. Mobile wireless devices can providecapabilities to communicate with wireless networks based on two or moredifferent wireless communication technologies, e.g. GSM and UMTS, UMTSand LTE, or CDMA 2000 1× and LTE. Newer wireless network technologiescan offer advanced capabilities, while legacy wireless networktechnologies can provide greater geographic area coverage and/ordifferent wireless service implementations. Wireless networks and mobilewireless devices that offer communication capabilities for multiplewireless network technologies can provide in parallel a wider range ofservices and greater coverage.

It should be understood that implementations of the same methods andapparatuses described herein can apply to mobile wireless devices thatoperate in different types of wireless networks, particularly one ormore wireless networks that offer connections using two or moredifferent generations or types of wireless communication protocols. Forexample, the same teachings can be applied to a combination of LTE andGSM networks, LTE and UMTS networks, LTE and CDMA 2000 1× networks orother “combined” multiple radio access technology (multi-RAT) wirelessnetworks.

LTE wireless networks can provide for packet switched (PS) connectionswith mobile wireless devices, with a voice connection supported througha voice-over-LTE (VoLTE) service using a PS connection; however, someLTE wireless networks may not support VoLTE services. In addition, LTEwireless network technology will be installed over many years, andtherefore wireless network operators will continue to operate wirelessnetworks supporting legacy wireless network technologies in parallelwith wireless networks using newer LTE wireless network technology. Toensure a mobile wireless device can establish voice connections usinglegacy technologies in parallel with newer LTE wireless networktechnology, the LTE wireless communication protocol includes a CSFBprocedure so that the mobile wireless device can switch from the LTEwireless network to a legacy wireless network. To receive a mobileterminated voice connection over a legacy wireless network, the mobilewireless device is notified of the incoming voice connection in order toswitch from the LTE wireless network to the legacy wireless network.When the mobile wireless device is in an RRC idle state, the LTEwireless network can send a paging message to the mobile wireless deviceindicating an incoming voice call. The paging message can include aparticular information element (IE) containing a core network (CN)domain parameter that indicates that a page to establish a voiceconnection originates from a circuit switched (CS) domain. The mobilewireless device and the LTE wireless network can exchange a series ofsignaling messages that ultimately redirect the mobile wireless deviceto disconnect from the LTE wireless network and connect to a legacywireless network through which a CS voice connection can be established.When the mobile wireless device is in an RRC connected state, the LTEwireless network can be precluded from sending a paging message havingthe CN domain parameter set to the CS domain. Instead, the LTE wirelessnetwork can send a CS service notification message to the mobilewireless device, and again after an exchange of signaling messages, themobile wireless device can be redirected from the LTE wireless networkto a legacy wireless network over which to establish a CS voiceconnection. If the mobile wireless device, however, is in an RRCconnected state, a paging message having the CN domain parameter set tothe CS domain sent by the LTE wireless network to the mobile wirelessdevice can be ignored, and the mobile wireless device can missestablishing an intended mobile terminated voice connection over alegacy wireless network. The LTE wireless network can send the pagingmessage with the CS domain set to the mobile wireless device instead ofthe CS service notification message in certain circumstances, e.g., whena connected state of the mobile wireless device at the mobile wirelessdevice differs from a connected state of the mobile wireless device atthe LTE wireless network.

Several scenarios described further herein illustrate circumstances inwhich the state of a connection between the mobile wireless device andthe LTE wireless network can be misaligned. In some circumstances, aninternal state of the mobile wireless device can be in an RRC connectedstate, while the LTE wireless network can consider the mobile wirelessdevice to be in an RRC idle state. In this case, the mobile wirelessdevice would expect a CS service notification message to initiate a CSFBprocedure (as for an RRC connected state) rather than a paging messagewith CS domain set (as for an RRC idle state). In response to anindication from a legacy wireless network of an incoming mobileterminated voice connection, the LTE wireless network can send a pagingmessage having the CN domain parameter set to the CS domain, as the LTEwireless network can consider the mobile wireless device to be in an RRCidle state. In a representative embodiment, the mobile wireless devicecan undertake one or more actions to realize a CSFB procedure when a setof conditions is met in order to properly receive and process the pagingmessage received from the LTE wireless network. In an embodiment, themobile wireless device can identify when the paging message includes auser equipment (UE) identity IE that indicates that the paging messageis intended for the particular mobile wireless device, i.e., the UEidentity IE of the paging message uniquely identifies the particularmobile wireless device. The mobile wireless device can also identifythat the CN domain IE of the paging message is set to a CS domain. Themobile wireless device can further determine that the paging message isnot identified as a public warning system (PWS) notification, e.g., nota commercial mobile alert service (CMAS) paging message and not anearthquake and tsunami warning system (ETWS) paging message. When thereceived paging message is confirmed to meet this set of conditions, themobile wireless device, even when in an RRC connected state, can respondto the received paging message having the CN domain set to CS toinitiate a CSFB procedure.

In a representative embodiment, the mobile wireless device in an RRCconnected state responds to the received paging message that indicatesorigination from a CS domain by releasing the RRC connection to the LTEwireless network, e.g., releasing an “internal” state of the mobilewireless device from the LTE wireless network and returning the“internal” state of the mobile wireless device to an RRC idle state. Themobile wireless device can subsequently respond to the received pagingmessage using a sequence of signaling messages identical to or similarto those signaling messages that would be used when receiving the samepaging message when in an RRC idle state. The mobile wireless device canestablish a new RRC connection with the LTE wireless network. The mobilewireless device can send an extended service request message thatprovides a positive CSFB response indication to the LTE wirelessnetwork. The LTE wireless network, in response to the extended servicerequest message, can release the new RRC connection and redirect themobile wireless device to a legacy wireless network, e.g., a 2G/2.5G/3G(non-LTE) radio access network. The mobile wireless device can “camp” onthe legacy wireless network and respond to the paging message indirectlyreceived from the legacy wireless network in order to establish a mobileterminated CS voice connection through the legacy wireless network.

In another representative embodiment, the mobile wireless device in anRRC connected state can respond to a received paging message thatindicates origination from a CS domain by sending an extended servicerequest message that includes a positive CSFB response indication to theLTE wireless network (e.g., responding in a similar manner as whenresponding to receiving a CS service notification message from the LTEwireless network). If the LTE wireless network responds to the extendedservice request with an RRC connection release message that includesredirection to a legacy wireless network, the mobile wireless device canrelease the RRC connection with the LTE wireless network and camp on thelegacy non-LTE wireless network. The mobile wireless device can respondto the paging message received indirectly from the legacy non-LTEwireless network to establish a mobile terminated CS voice connectionover the legacy non-LTE wireless network. If the LTE wireless networkdoes not positively acknowledge the extended service request sent by themobile wireless device, then the mobile wireless device can “locally”release the RRC connection (e.g., by changing an “internal” stateparameter) and proceed to establish a second RRC connection with the LTEwireless network followed sending by a second extended service requestmessage that indicates a positive CSFB response to the LTE wirelessnetwork as described above. If the LTE wireless network positivelyacknowledges the second extended service request message with aredirection indication, then the mobile wireless device can release thesecond RRC connection and subsequently camp on and connect to the legacywireless network in order to complete a voice connection through thelegacy wireless network.

FIG. 1 illustrates a representative generic wireless network 100 thatcan include multiple mobile wireless devices 102 connected by radiolinks 126 to radio sectors 104 provided by a radio access network 128.Each radio sector 104 can represent a geographic area of radio coverageemanating from an associated radio node 108 using a radio frequencychannel operating at a selected frequency. Each radio node 108 cangenerate one or more radio sectors 104 to which the mobile wirelessdevice 102 can connect by one or more radio links 126. In some wirelessnetworks 100, the mobile wireless device 102 can be connected to morethan one radio sector 104 simultaneously. The multiple radio sectors 104to which the mobile wireless device 102 can be connected can emanatefrom a single radio node 108 or from separate radio nodes 108 that canshare a common radio controller 110. A group of radio nodes 108 togetherwith the associated radio controller 110 can be referred to as a radioaccess subsystem 106. Typically each radio node 108 in a radio accesssubsystem 106 can include a set of radio frequency transmitting andreceiving equipment mounted on an antenna tower, and the radiocontroller 110 connected to the radio nodes 108 can include electronicequipment for controlling and processing transmitted and received radiofrequency signals. The radio controller 110 can manage theestablishment, maintenance and release of the radio links 126 thatconnect the mobile wireless device 102 to the radio access network 128.The radio controller 110 and/or the radio nodes 108 can exchangemessages with the mobile wireless devices 102 to establish connectionsand to release connections. The radio controller 110 and/or the radionodes 108 can generate messages as well as forward messages receivedfrom other radio access subsystems 106 or other network elements of thegeneric wireless network 100.

Radio resources that form the radio links 126 in the radio sectors 104can be shared among multiple mobile wireless devices 102 using a numberof different multiplexing techniques, including time division, frequencydivision, code division, space division and combinations thereof. Aradio resource control (RRC) signaling connection can be used tocommunicate between the mobile wireless device 102 and the radiocontroller 110 in the radio access subsystem 106 of the radio accessnetwork 128 including requests for and dynamic allocations of radioresources to multiple mobile wireless devices 102.

The radio access network 128, which provides radio frequency air linkconnections to the mobile wireless device 102, connects also to a corenetwork 112 that can include a circuit switched domain 122, usually usedfor voice traffic, and a packet switched domain 124, usually used fordata traffic. Radio controllers 110 in the radio access subsystems 106of the radio access network 128 can connect to both a circuit switchingcenter 118 in the circuit switched domain 122 and a packet switchingnode 120 in the packet switched domain of the core network 112. Thecircuit switching center 118 can route circuit switched traffic, such asa voice call, to a public switched telephone network (PSTN) 114. Thepacket switching node 120 can route packet switched traffic, such as a“connectionless” set of data packets, to a public data network (PDN)116.

FIG. 2 illustrates a representative CDMA 2000 1× wireless network 200that can include elements comparable to those described for the genericwireless network 100 shown in FIG. 1. Multiple mobile stations 202 canconnect to one or more radio sectors 204 through radio frequency links226. Each radio sector 204 can radiate outward from a base transceiverstation (BTS) 208 that can connect to a base station controller (BSC)210, together forming a base station subsystem (BSS) 206. Multiple basestation subsystems 206 can be aggregated to form a radio access network228. Base station controllers 210 in different base station subsystems206 can be interconnected. The base station controllers 210 can connectto both a circuit switched domain 222 that use multiple mobile switchingcenters (MSC) 218 and a packet switched domain 224 formed with packetdata service nodes (PDSN) 220, which together can form a core network212 for the wireless network 200. As with the generic wireless network100 described above, the circuit switched domain 222 of the core network212 can interconnect to the PSTN 114, while the packet switched domain224 of the core network 212 can interconnect to the PDN 116.Establishing connections on the CDMA 2000 1× wireless network 200 candepend on the mobile station 202 receiving a page from the BSS 206indicating an incoming connection. The mobile station 202 can listen forpages during specific paging intervals.

FIG. 3 illustrates a representative Long Term Evolution (LTE) wirelessnetwork 300 architecture designed as a packet switched networkexclusively. A mobile terminal 302 can connect to an evolved radioaccess network 322 through radio links 326 associated with radio sectors304 that emanate from evolved Node B's (eNodeB) 310. The eNodeB 310includes the functions of both transmitting and receiving base stations(such as the BTS 208 in the CDMA 2000 1× wireless network 200) as wellas base station radio controllers (such as the BSC 210 in the CDMA 20001× wireless network 200). The equivalent core network of the LTEwireless network 300 is an evolved packet core network 320 includingserving gateways 312 that interconnect the evolved radio access network322 to public data network (PDN) gateways 316 that connect to externalinternet protocol (IP) networks 318. Multiple eNodeB 310 can be groupedtogether to form an evolved UMTS radio access network (eUTRAN) 306. TheeNodeB 310 can also be connected to a mobility management entity (MME)314 that can provide control over connections for the mobile terminal302.

FIG. 4 illustrates a mobile wireless device 102 in communication withboth the LTE wireless network 300 and with the CDMA 2000 1× wirelessnetwork 200. The CDMA 2000 1× wireless network 200 can connect to thecircuit switch based public switched telephone network (PSTN) 114through a mobile switching center (MSC) 218. The MSC 218 of the CDMA2000 1× wireless network 200 can be interconnected to the MME 314 of theLTE wireless network 300 to coordinate call signaling for the mobilewireless device 102. In some embodiments, the CDMA 2000 1× wirelessnetwork 200 can seek to establish a connection through the radio links226 with the mobile wireless device 102, e.g. to establish a voiceconnection between the mobile wireless device 102 and the PSTN 114. Ifthe mobile wireless device 102 is connected to the CDMA 2000 1× wirelessnetwork 200, then the CDMA 2000 1× wireless network 200 can transmit apaging message to the mobile wireless device 102 using the radio links226 to indicate the availability of an incoming voice connection. Whenthe mobile wireless device 102 is connected to the LTE wireless network300, the CDMA 2000 1× wireless network can indicate an incoming voicecall by providing an indication of the incoming voice call from the MSC218 to the MME 314 of the LTE wireless network 300. The LTE wirelessnetwork 300 can then communicate an appropriate message to the mobilewireless device 102 to disconnect from the LTE wireless network 300 and“fall back” to the circuit switched CDMA 2000 1× wireless network 200 inorder to receive the mobile terminated CS voice connection.

Representative embodiments of mobile wireless devices can connect tocombinations of wireless networks that use different wirelesstechnologies, in addition to those described above, and the embodimentsdescribed herein are not limited to the specific combination illustratedby FIG. 4. In particular, representative embodiments include mobilewireless devices that can communicate over the LTE wireless network 300and over a GSM or UMTS wireless network. Other combinations of an LTEwireless network 300 and a wireless network using an earlier generation“legacy” wireless communication technology are also contemplated.

FIG. 5 illustrates a representative single chip wirelesstransmitter/receiver 514 that can reside in a mobile wireless device 102that can communicate with the LTE wireless network 300 or with the CDMA2000 1× wireless network 200 separately but not simultaneously. Whenconnected to the LTE wireless network 300, the single chip mobilewireless device 102 can use a single transmitter (Tx) 508 and dualreceivers (Rx) 510/512. When connected to the CDMA 2000 1× wirelessnetwork 200, the single chip mobile wireless device 102 can use thesingle transmitter 508 and either one receiver (Rx 510 or Rx 512) ordual receivers (Rx 510 and Rx 512). Use of dual receivers for both theLTE wireless network 300 and the CDMA 2000 1× wireless network 200 canprovide higher receive signal quality and therefore higher datathroughput and/or greater connection reliability under adverse signalconditions. An interconnect block 506 can allow either an LTE signalprocessing 502 block or a CDMA 2000 1× signal processing block 504 totransmit and receive radio signals through the transmitter 508 and oneor both of the receivers 510/512 respectively. Within the single chipwireless mobile wireless device 102, the single chip wirelesstransmitter/receiver 514 can be connected to one or more processors (notshown), e.g., an application processor, that can perform “higher layer”functions such as establishing connections for applications and formingmessages to be communicated with various wireless networks, while thesingle chip wireless transmitter/receiver 514 can perform “lower layer”functions such as ensuring integrity of transmitted and received radiofrequency signals that carry messages for the application processor.

FIG. 6 illustrates another representative single chip wirelesstransmitter/receiver 614 that can reside in a mobile wireless device 102that can communicate with the LTE wireless network 300 or with a non-LTEwireless network (e.g., a legacy wireless network), separately but notsimultaneously. When connected to the LTE wireless network 300, thesingle chip mobile wireless device 102 that contains the single chiptransmitter/receiver 614 can use one or more transmitters 608 and one ormore receivers 610 for communication with either the LTE wirelessnetwork 300 or the non-LTE wireless network. In some embodiments, themobile wireless device 102 can include an LTE processing block 602 thatcan be connected through an interconnect 606 to all or a subset of thetransmitters 608 and receivers 610. The mobile wireless device 102 canalso include a non-LTE processing block 604 that can also be connectedthrough the interconnect 606 to all or a second subset of thetransmitters 607 and receivers 610. The mobile wireless device 102 canre-use hardware elements, e.g., transmit and/or receive signalingchains, for two different wireless networks to which the mobile wirelessdeice 102 can be connected. The mobile wireless device 102 can beconnected to the LTE wireless network 300 for PS data connections andcan be separately connected to a non-LTE wireless network (e.g., a GSMwireless network, a UMTS wireless network, or the CDMA 2000 1× wirelessnetwork 200) for CS voice connections. The mobile wireless device 102can be preferably connected to the LTE wireless network 300 to realizehigher throughput data connections and revert to the non-LTE wirelessnetwork when required to originate or terminate CS voice connections,e.g., when the LTE wireless network 300 and/or the mobile wirelessdevice 102 does not support VoLTE type connections. In some embodiments,the mobile wireless device 102 obtains one or more signaling messagesfrom the LTE wireless network 300 that directs the mobile wirelessdevice 102 to connect to the non-LTE wireless network, e.g., to receivean incoming CS voice call.

FIG. 7 illustrates a prior art sequence 700 of messages exchangedbetween the mobile wireless device 102 and the LTE wireless network 300for a CSFB procedure. Initially, in block 702, the mobile wirelessdevice 102 can be camped on (registered with) the LTE wireless network300. The mobile wireless device 102 can also be attached to the LTEwireless network 300 but not be connected to the LTE wireless network300, i.e., no active RRC connection can exist between the mobilewireless device 102 and the LTE wireless network 300. Thus, both themobile wireless device 102 and the LTE wireless network 300 can considerthe connection state between them to be an RRC idle state. In block 704,the LTE wireless network 300 can obtain an indication of an incoming CSvoice call for a non-LTE wireless network, i.e., the non-LTE wirelessnetwork can seek to form a CS connection with the mobile wireless device102 to establish a mobile terminated voice call. As the LTE wirelessnetwork 300 considers the mobile wireless device 102 to be in an RRCidle state, the LTE wireless network 300 can send a paging message 706to the mobile wireless device 102. The paging message 706 can include aninformation element indicating a core network domain from which thepaging message 706 originates as a circuit switched (CS) domain. As themobile wireless device 102 is in an RRC idle state, in response to thepaging message 706, the mobile wireless device 102 can respond bysending an RRC connection request 708 to establish an RRC connectionwith the LTE wireless network 300. The LTE wireless network 300 canrespond by sending an RRC connection setup message 710 to the mobilewireless device 102. In response, the mobile wireless device 102 cansend an RRC connection setup complete message 712. Further in responseto the paging message 706 that indicated the CS domain origination, themobile wireless device 102 can send an extended service request with theRRC connection setup complete message that includes a positive CSFBindication. The mobile wireless device 102 can indicate to the LTEwireless network 300 an agreement to switch to a non-LTE wirelessnetwork in order to complete a connection over the CS non-LTE wirelessnetwork. The LTE wireless network 300 can respond by sending an RRCconnection release message 714 that includes a redirection of the mobilewireless device 102 to the non-LTE wireless network. In block 716, themobile wireless device 102 can switch away from the LTE wireless network300 to camp on the non-LTE wireless network. Subsequently, the mobilewireless device 102 can provide a paging response 718 to the non-LTEwireless network. The mobile wireless device 102 can then establish aconnection through the non-LTE wireless network to complete a mobileterminated voice connection through the non-LTE wireless network.

FIG. 8 illustrates another prior art sequence 800 of messages exchangedbetween the mobile wireless device 102 and the LTE wireless network 300for a CSFB procedure. Initially, in block 802, the mobile wirelessdevice 102 can be camped on (registered with) the LTE wireless network300. The mobile wireless device 102 can also be attached to the LTEwireless network 300 but not be connected to the LTE wireless network300, i.e., no active RRC connection can exist between the mobilewireless device 102 and the LTE wireless network 300. Thus, both themobile wireless device 102 and the LTE wireless network 300 can considerthe connection state between them to be an RRC idle state. In block 804,the LTE wireless network 300 can initiate a data connection with themobile wireless device 102. The LTE wireless network 300 can send apaging message 806 to the mobile wireless device 102. The paging message806 can include an information element indicating a core network domainfrom which the paging message 806 originates as a packet switched (PS)domain. As the mobile wireless device 102 is in an RRC idle state, inresponse to the paging message 806, the mobile wireless device 102 canrespond by sending an RRC connection request 808 to establish an RRCconnection with the LTE wireless network 300. The LTE wireless network300 can respond by sending an RRC connection setup message 810 to themobile wireless device 102. In response, the mobile wireless device 102can send an RRC connection setup complete message 812. The mobilewireless device 102 can further include a service request with the RRCconnection setup complete message 812. In block 814, the LTE wirelessnetwork 300 and the mobile wireless device 102 can set up radio accessbearers and initiate a transfer of packet switched data using the radioaccess bearers. During the active PS data connection, in block 816, theLTE wireless network 300 can receive an indication of an incoming CSvoice call for a non-LTE wireless network, i.e., the non-LTE wirelessnetwork can seek to form a CS connection with the mobile wireless device102 to establish a mobile terminated voice call. As the LTE wirelessnetwork 300 considers the mobile wireless device 102 to be in an RRCconnected state, the LTE wireless network 300 can send a CS servicenotification 818 to the mobile wireless device 102. As the mobilewireless device 102 is in an RRC connected state, in response to the CSservice notification 818, the mobile wireless device 102 can send an RRCconnection setup complete message 820 that includes an extended servicerequest with a positive CSFB response indication to the LTE wirelessnetwork 300. The LTE wireless network 300 in response can send an RRCconnection release message 822 to the mobile wireless device 102, theRRC connection release message 822 indicating redirection of the mobilewireless device 102 from the LTE wireless network 300 to a non-LTEwireless network. In block 824, the mobile wireless device 102 canswitch away from the LTE wireless network 300 to camp on the non-LTEwireless network. Subsequently, the mobile wireless device 102 canprovide a paging response 826 to the non-LTE wireless network. Themobile wireless device 102 can then establish a connection through thenon-LTE wireless network to complete a mobile terminated voiceconnection through the non-LTE wireless network.

FIGS. 7 and 8 illustrated successful signaling message exchanges betweenthe LTE wireless network 300 and the mobile wireless device 102 thatresulted in a mobile terminated CS connection over the non-LTE wirelessnetwork using a CSFB procedure. In some circumstances, the mobilewireless device 102 and the LTE wireless network 300 can becomemisaligned with respect to the RRC connection state, which can result inan unsuccessful attempt to establish a CS connection through a CSFBprocedure. FIG. 9 provides an example of this misalignment.

FIG. 9 illustrates a prior art signaling message exchange 900 betweenthe mobile wireless device 102 and the LTE wireless network 300. Inblock 902, the mobile wireless device 102 can be connected to andactively transferring data with the LTE wireless network 300. In block904, during the active data transfer, the LTE wireless network 300 canreceive an indication of an incoming CS voice call for a non-LTEwireless network, i.e., the non-LTE wireless network can seek to form aCS connection with the mobile wireless device 102 to establish a mobileterminated voice call. In block 906, the LTE wireless network 300 andthe mobile wireless device 102 can lose their connection, e.g., due to aradio link failure between them. The mobile wireless device 102 and theLTE wireless network 300 can respond to the radio link failuredifferently (e.g., with different response times). In block 908, the LTEwireless device 300 can release the RRC connection with the mobilewireless device 102. In block 910, the mobile wireless device 102 cancontinue to be connected to (or seeking to re-establish a connectionwith) the LTE wireless network 300. The mobile wireless device 102 cancontinue to be in an RRC connected state (internal to the mobilewireless device 102), while the LTE wireless network 300 can considerthe mobile wireless device 102 to be in an RRC idle state (havingsevered the RRC connection). In response to the incoming voiceconnection from the non-LTE wireless network in block 904, the LTEwireless network 300 can send a paging message with a core networkdomain IE set to a CS domain (as the LTE wireless network 300 considersthe mobile wireless device 102 to be in an RRC idle state). The mobilewireless device 102, however, in block 914, can ignore the pagingmessage from the LTE wireless network 300, as the paging message can bedisallowed in the RRC connected state. With this sequence of eventsillustrated in FIG. 9, the mobile wireless device 102 can miss theattempt to form a CS voice connection communicated by the LTE wirelessnetwork 300 using the paging message 912. FIG. 9 provides an example inwhich misaligned connection states between the mobile wireless device102 and the LTE wireless network 300 can result in an unsuccessful CSFBprocedure.

FIG. 9 illustrates a scenario in which an RRC connection release messagecan be sent by the LTE wireless network 300 to the mobile wirelessdevice 102, and because of poor radio conditions, the mobile wirelessdevice 102 does not receive the RRC connection release message. The LTEwireless network 300 can locally release the RRC connection to themobile wireless device 102 after a timer expires, thereby transitioningthe mobile wireless device 102 to an RRC idle state. The mobile wirelessdevice 102 can remain locally in an RRC connected state, as the mobilewireless device 102 did not receive the RRC connection release message.As shown in FIG. 9, the LTE wireless network 300 can transmit a pagingmessage to initiate a CSFB procedure with the mobile wireless device102, as the LTE wireless network 300 considers the mobile wirelessdevice 102 to be in an RRC idle state. The mobile wireless device 102,which remains locally in an RRC connected state, ignores the pagingmessage, as the paging message is not valid in an RRC connected state.In accordance with the 3GPP LTE wireless protocol specification, validpaging messages in an RRC connected state are restricted to (1) systeminformation modification notifications, (2) public warning system (PWS)type messages, including CMAS and ETWS messages. Paging messages withthe CS domain set are not allowed in the LTE RRC connected state, andthus the mobile wireless device 102 may ignore such messages.

In addition to the scenario described above for FIG. 9, other scenarioscan arise in which the mobile wireless device 102 and the LTE wirelessnetwork 300 become misaligned with regard to connection states and/orcommunicated messages, the misalignment potentially resulting in afailed CSFB procedure. In one scenario, a radio link failure between theLTE wireless network 300 and the mobile wireless device 102 can resultin a loss of one or more packet transmissions sent by the LTE wirelessnetwork 300 to the mobile wireless device 102. For example, the LTEwireless network 300 can send one or more radio link control (RLC)packet data units (PDUs), which can be not received by the mobilewireless device 102. As a result, the LTE wireless network can receiveno acknowledgement (ACK) responses to the RLC PDUs. After a number ofretries and/or timer expirations, the LTE wireless network 300 canlocally release the RRC connection to the mobile wireless device 102,while the mobile wireless device 102, which is not receiving the datapackets or other signaling messages due to the radio link failure, canremain locally in an RRC connected state. The LTE wireless network 300and the mobile wireless device 102 can end up with misaligned connectionstates.

In a further scenario, a race condition can occur between an RRCconnection setup message sent by the eUTRAN of the LTE wireless network300 to the mobile wireless device 102 and a paging message with the CSdomain indication sent by the evolved packet core network 320 of the LTEwireless network 300. The MME 314 of the evolved packet core network 320can receive a paging indication from a non-LTE wireless network, e.g.,the MSC 218 of the CDMA 2000 1× wireless network 200, and communicatethe paging message to the eNodeB 310 to send to the mobile wirelessdevice 102. The paging message, which can assume the mobile wirelessdevice 102 is in an idle state, can be in conflict with the RRCconnection setup message that initiates transition to an RRC connectedstate. The LTE wireless network 300 can send the paging message with thecore network domain information element set to the circuit switcheddomain to the mobile wireless device 102 before receiving a response tothe RRC connection setup message, i.e., before receiving the RRCconnection setup complete message from the mobile wireless device 102.The mobile wireless device 102, however, can receive the paging messagewith CS domain after sending the RRC connection setup complete messageto the LTE wireless network 300. As a result, the LTE wireless network300 sends the paging message while still in an RRC idle state (RRCconnection not completed), while the mobile wireless device 102 receivesthe paging message while in an RRC connected state. The mobile wirelessdevice 102 in the RRC connected state can ignore the paging messagehaving the CS domain set, and thus the CSFB procedure can fail.

In representative embodiments, the mobile wireless device 102 can accepta paging message having a core network domain information element set tothe CS domain while in an RRC connected state when certain additionalconditions are met. The mobile wireless device 102 can undertake one ormore different actions after accepting the paging message that canresult in a successful CSFB procedure.

FIG. 10 illustrates a representative embodiment of a method 1000 torespond to paging messages received from a first wireless network by amobile wireless device 102. In step 1002, the mobile wireless device 102can receive a paging message from the first wireless network. In step1004, the mobile wireless device 102 can determine whether the pagingmessage uniquely identifies the mobile wireless device 102, e.g.,includes a first information element that contains a parameter thatuniquely identifies the particular mobile wireless device 102. In step1006, the mobile wireless device 102 determines whether the pagingmessage originates from a second wireless network different from thefirst wireless network, e.g., contains a second information elementindicating origination of the paging message from the second wirelessnetwork. In step 1008, the mobile wireless device 102 determines whetherthe paging message is not a public warning system message, e.g., doesnot include a third information element that indicates that the pagingmessage is a public warning message. In step 1010, when an internalstate of the mobile wireless device 102 indicates that the mobilewireless device 102 is not connected to the first wireless network,e.g., in an RRC idle state, the method ends. In step 1010, when theinternal state of the mobile wireless device 102 indicates that themobile wireless device 102 is connected to the first wireless network,e.g., in an RRC connected state, the method continues. In step 1012, themobile wireless device 102, disconnects from the first wireless network.In step 1014, the mobile wireless device 102 establishes a connection tothe second wireless network.

In a representative embodiment of the method illustrated in FIG. 10, thepaging element includes a second information element that indicates thesecond wireless network is a circuit switched (CS) network, and thefirst wireless network is a packet switched (PS) network. In anotherrepresentative embodiment, the public warning system message is acommercial mobile alert service (CMAS) message or an earthquake andtsunami warning system (ETWS) message. In a representative embodiment,the paging message includes a first information element that includes amobile subscriber identity that uniquely identifies the mobile wirelessdevice 102, e.g., a temporary mobile subscriber identity (TMSI) orinternational mobile subscriber identity (IMSI). In an embodiment, thefirst wireless network operates according to a long-term evolution (LTE)wireless communication protocol, and the second wireless networkoperates according to a non-LTE wireless communication protocol. In anembodiment, the paging message includes an indication of an incomingmobile terminated voice call for the mobile wireless device 102 to becompleted over the second wireless network.

FIG. 11 illustrates a representative embodiment of method steps 1100 todisconnect the mobile wireless device from the first wireless networkapplicable to the method of FIG. 10. In a representative embodiment, themethod step 1012 of the method illustrated in FIG. 10 includes one ormore of the steps illustrated in FIG. 11. In step 1102, the mobilewireless device 102 releases a first radio resource control (RRC)connection to the first wireless network, e.g., by changing an internalstate of the mobile wireless device 102. In step 1104, the mobilewireless device 102 establishes a second RRC connection with the firstwireless network. By releasing the RRC connection in step 1102, themobile wireless device 102 returns to an RRC idle state. To respond tothe paging message received from the first wireless network, the mobilewireless device 102 then establishes anew a second RRC connection to thefirst wireless network. In step 1106, the mobile wireless device 102sends an extended service request message to the first wireless network,the extended service request message including an indication of apositive CSFB response to the received paging message. In step 1108, themobile wireless device 102 receives a signaling message from the firstwireless network, the signaling message indicating a release of thesecond RRC connection to the first wireless network and also including aredirection of the mobile wireless device 102 from the first wirelessnetwork to the second wireless network.

FIG. 12 illustrates another representative embodiment of method steps todisconnect the mobile wireless device from the first wireless networkapplicable to the method of FIG. 10. In a representative embodiment, themethod step 1012 of the method illustrated in FIG. 10 includes one ormore of the steps illustrated in FIG. 12. In step 1202, the mobilewireless device 102 sends a first extended service request message tothe first wireless network, the first extended service request messageindicating a positive circuit switched fallback (CSFB) response to thereceived paging message. In step 1204, the mobile wireless device 102can determine whether a first signaling message indicating redirectionof the mobile wireless device 102 to a second wireless network isreceived from the first wireless network in response to the firstextended service request message. If the mobile wireless device 102receives a response from the first wireless network to the firstextended service request message, then the mobile wireless device 102can release a first RRC connection to the first wireless network in step1216 and end this portion of the method. If the mobile wireless device102 does not receive a response from the first wireless network to thefirst extended service request message, in step 1206, the mobilewireless device 102 can release the first RRC connection to the firstwireless network and subsequently establish a new second RRC connectionto the first wireless network in step 1208. Having established thesecond RRC connection to the first wireless network, the mobile wirelessdevice 102 can, in step 1210, send a second extended service requestmessage to the first wireless network, the second extended servicerequest message including a positive CSFB response indication. In step1212, the mobile wireless device 102 can receive a second signalingmessage from the first wireless network, the second signaling messageindicating a redirection of the mobile wireless device 102 to the secondwireless network. In step 1214, the mobile wireless device 102 canrelease the second RRC connection to the first wireless network. In anembodiment, having released the first RRC connection and/or the secondRRC connection to the first wireless network and having received aresponse from the first wireless network to the extended servicerequest, the response redirecting the mobile wireless device 102 to thesecond wireless network, the mobile wireless device 102 can subsequentlyestablish a connection through the second wireless network, e.g., toestablish a mobile terminated voice connection.

FIG. 13 illustrates a representative embodiment of method steps toestablish a connection between the mobile wireless device and a secondwireless network applicable to the method of FIG. 10. In an embodiment,the mobile wireless device executes the steps of FIG. 13 followingeither the steps of FIG. 11 or the steps of FIG. 12. In a representativeembodiment, the method step 1014 of the method illustrated in FIG. 10includes one or more of the steps illustrated in FIG. 13. In step 1302,the mobile wireless device 102 sends a paging response message to thesecond wireless network. In step 1304, the mobile wireless device 102establishes a circuit switched voice connection over the second wirelessnetwork.

Software, hardware, or a combination of hardware and software canimplement various aspects of the described embodiments. The describedembodiments can also be encoded as computer program code on anon-transitory computer readable medium. The non-transitory computerreadable medium is any data storage device that can store data that canthereafter be read by a computer system. Examples of the non-transitorycomputer readable medium include read-only memory, random-access memory,CD-ROMs, HDDs, DVDs, magnetic tape and optical data storage devices. Thecomputer program code can also be distributed over network-coupledcomputer systems so that the computer program code is stored andexecuted in a distributed fashion.

The various aspects, embodiments, implementations or features of thedescribed embodiments can be used separately or in any combination. Theforegoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of the specificembodiments described herein are presented for purposes of illustrationand description. They are not targeted to be exhaustive or to limit theembodiments to the precise forms disclosed. It will be apparent to oneof ordinary skill in the art that many modifications and variations arepossible in view of the above teachings.

The advantages of the embodiments described are numerous. Differentaspects, embodiments or implementations can yield one or more of thefollowing advantages. Many features and advantages of the presentembodiments are apparent from the written description and, thus, it isintended by the appended claims to cover all such features andadvantages of the invention. Further, since numerous modifications andchanges will readily occur to those skilled in the art, the embodimentsshould not be limited to the exact construction and operation asillustrated and described. Hence, all suitable modifications andequivalents can be resorted to as falling within the scope of theinvention.

What is claimed is:
 1. A method to respond to paging messages by amobile wireless device, the method comprising: by the mobile wirelessdevice; receiving a paging message from a first wireless network;determining that the paging message includes a first information elementuniquely identifying the mobile wireless device; determining that thepaging message includes a second information element indicating that thepaging message originates from a second wireless network; determiningthat the paging message does not include a third information elementindicating the paging message is a public warning system message; andwhen an internal state of the mobile wireless device indicates themobile wireless device is connected to the first wireless network, afterreceiving the paging message and after determining the paging messageincludes the first and second information elements and does not includethe third information element, disconnecting the mobile wireless devicefrom the first wireless network and establishing a connection of themobile wireless device to the second wireless network.
 2. The methodrecited in claim 1, wherein the second information element indicates thesecond wireless network is a circuit switched (CS) network, and thefirst wireless network is a packet switched (PS) network.
 3. The methodrecited in claim 1, wherein the public warning system message is acommercial mobile alert service (CMAS) message or an earthquake andtsunami warning system (ETWS) message.
 4. The method recited in claim 1,wherein the first information element includes a mobile subscriberidentity that uniquely identifies the mobile wireless device.
 5. Themethod recited in claim 1, wherein the first wireless network operatesaccording to a long term evolution (LTE) wireless communicationprotocol, and the second wireless network operates according to anon-LTE wireless communication protocol.
 6. The method recited in claim1, wherein the paging message includes an indication of an incomingmobile terminated voice call for the mobile wireless device to becompleted over the second wireless network.
 7. The method recited inclaim 1, wherein disconnecting the mobile wireless device from the firstwireless network comprises releasing a first radio resource control(RRC) connection to the first wireless network locally in the mobilewireless device.
 8. The method recited in claim 7, wherein disconnectingthe mobile wireless device from the first wireless network furthercomprises: establishing a second RRC connection between the mobilewireless device and the first wireless network; sending an extendedservice request message to the first wireless network, the extendedservice request message indicating a positive circuit switched fallback(CSFB) response to the paging message; and receiving a signaling messagefrom the first wireless network, the signaling message indicatingrelease of the second RRC connection and redirection of the mobilewireless device to the second wireless network.
 9. The method recited inclaim 1, wherein establishing the connection of the mobile wirelessdevice to the second wireless network comprises: sending a pagingresponse message to the second wireless network; and establishing acircuit switched voice connection over the second wireless network. 10.The method recited in claim 1, wherein disconnecting the mobile wirelessdevice from the first wireless network comprises: sending a firstextended service request message to the first wireless network, thefirst extended service request message indicating a first positivecircuit switched fallback (CSFB) response to the paging message; whenreceiving a first signaling message from the first wireless network inresponse to the first extended service request message, the firstsignaling message redirecting the mobile wireless device to the secondwireless network, releasing a first radio resource control (RRC)connection of the mobile wireless device to the first wireless network;and when not receiving the first signaling message from the firstwireless network in response to the first extended service requestmessage, releasing the first RRC connection of the mobile wirelessdevice to the first wireless network, establishing a second RRCconnection to the first wireless network, sending a second extendedservice request message to the first wireless network indicating asecond positive CSFB response to the paging message, receiving a secondsignaling message from the first wireless network in response to thesecond extended service request message redirecting the mobile wirelessdevice to the second wireless network, and in response to receiving thesecond signaling message, releasing the second RRC connection of themobile wireless device to the first wireless network.
 11. A mobilewireless device comprising: one or more processors configured to controlestablishing and releasing connections between the mobile wirelessdevice and a first wireless network and a second wireless network; oneor more transmitters configured to transmit signals to the firstwireless network according to a first wireless communication protocoland to the second wireless network according to a second wirelesscommunication protocol; and one or more receivers configured to receivesignals from the first and second wireless networks; wherein the one ormore processors are further configured to: obtain a paging messagereceived by the one or more receivers from the first wireless network;determine that the paging message includes a first information elementuniquely identifying the mobile wireless device; determine that thepaging message includes a second information element indicating thepaging message originates from the second wireless network; determinethat the paging message does not include a third information elementindicating that the paging message is a public warning system message;and disconnect the mobile wireless device from the first wirelessnetwork and establish a connection of the mobile wireless device to thesecond wireless network when (1) an internal state of the mobilewireless device indicates that the mobile wireless device is connectedto the first wireless network upon receipt of the paging message and (2)the paging message includes the first and second information elementsand does not include the third information element.
 12. The mobilewireless device recited in claim 11, wherein the second informationelement indicates the second wireless network is a circuit switched (CS)network, and the first wireless network is a packet switched (PS)network.
 13. The mobile wireless device recited in claim 11, wherein thepublic warning system message is a commercial mobile alert service(CMAS) message or an earthquake and tsunami warning system (ETWS)message.
 14. The mobile wireless device recited in claim 11, wherein thefirst information element includes a mobile subscriber identity thatuniquely identifies the mobile wireless device.
 15. The mobile wirelessdevice recited in claim 11, wherein the first wireless communicationprotocol is a long term evolution (LTE) wireless communication protocol,and the second wireless communication protocol is a non-LTE wirelesscommunication protocol.
 16. The mobile wireless device recited in claim11, wherein the paging message includes an indication of an incomingmobile terminated voice call for the mobile wireless device to becompleted over the second wireless network.
 17. The mobile wirelessdevice recited in claim 11, wherein disconnect the mobile wirelessdevice from the first wireless network comprises release a first radioresource (RRC) connection to the first wireless network locally in themobile wireless device.
 18. The mobile wireless device recited in claim17, wherein the one or more processors are further configured to:establish a second RRC connection between the mobile wireless device andthe first wireless network; provide to the one or more transmitters anextended service request message to send to the first wireless network,the extended service request message indicating a positive circuitswitched fallback (CSFB) response to the paging message; and obtain asignaling message received by the one or more receivers from the firstwireless network, the signaling message indicating release of the secondRRC connection and redirection of the mobile wireless device to thesecond wireless network.
 19. The mobile wireless device recited in claim11, wherein establish the connection of the mobile wireless device tothe second wireless network comprises: provide a paging response messageto the one or more transmitters to send to the second wireless network;and establish a circuit switched voice connection over the secondwireless network.
 20. The mobile wireless device recited in claim 11,wherein disconnect the mobile wireless device from the first wirelessnetwork comprises: provide a first extended service request message tothe one or more transmitters to send to the first wireless network, thefirst extended service request message indicating a first positivecircuit switched fallback (CSFB) response to the paging message; when afirst signaling message is received by the one or more receivers fromthe first wireless network in response to the first extended servicerequest message, the first signaling message redirecting the mobilewireless device to the second wireless network, release a first radioresource control (RRC) connection of the mobile wireless device to thefirst wireless network; and when the one or more receivers do notreceive the first signaling message from the first wireless network inresponse to the first extended service request message, release thefirst RRC connection of the mobile wireless device to the first wirelessnetwork, establish a second RRC connection to the first wirelessnetwork, provide to the one or more transmitters a second extendedservice request message to transmit to the first wireless network, thesecond extended service request message indicating a second positiveCSFB response to the paging message, obtain from the one or morereceivers a second signaling message received from the first wirelessnetwork in response to the second extended service request message, thesecond signaling message redirecting the mobile wireless device to thesecond wireless network, and in response to receipt of the secondsignaling message, releasing the second RRC connection of the mobilewireless device to the first wireless network.
 21. A computer programproduct encoded as computer program code in a non-transitory computerreadable medium for responding to paging messages by a mobile wirelessdevice, the computer program product comprising: computer program codefor receiving a paging message from a first wireless network; computerprogram code for determining that the paging message includes a firstinformation element uniquely identifying the mobile wireless device;computer program code for determining that the paging message includes asecond information element indicating that the paging message originatesfrom a second wireless network; computer program code for determiningthat the paging message does not include a third information elementindicating that the paging message is a public warning system message;and computer program code for, when an internal state of the mobilewireless device indicates that the mobile wireless device is connectedto the first wireless network upon receiving the paging message andafter executing the computer program code for determining that thepaging message includes the first and second information elements anddoes not include the third information element, disconnecting the mobilewireless device from the first wireless network and establishing aconnection of the mobile wireless device to the second wireless network.